An image sensing camera module (solid-state image sensing device) mounted, for example, to mobile phones integrally contains a solid-state image sensing element, an infrared filter, a wiring board with terminals, a lens, and a lens holder. The solid-state image sensing element may be a CCD (charge-coupled device) or a CMOS (complementary metal-oxide semiconductor) sensor IC (integrated circuit). Manufacturing processes have been progressively adapted for reducing the size of the solid-state image sensing element in step with the reduction in size of the camera module. In the increasingly more compact camera modules, fine dust (for example, 25 μm or larger) on an optical path can cause a defect in an image. The defect is a projection of the shadow of the dust appearing as dark spots or a stain on the image. The optical path in the camera module includes, for example, the light-receiving section (light-receiving plane) of the solid-state image sensing element and above a lid glass.
The dust which may cause image defects can be already attaching to a component of the camera module when the component is delivered to a module manufacturer, or may be produced during the manufacture of the module. Most of the dust that is attaching to components at the time of delivery is fine pieces of resin. Meanwhile, most of the dust that is produced during manufacture is metal and produced as a result of abrasion of manufacturing equipment (assembly devices) for the camera module.
The dust having this kind of origin and attaching to the optical path can be removed in an inspection immediately before shipment which is part of the manufacturing process of the camera module. However, the dust that is temporarily staying on any part other than the optical path is undetectable in the inspection immediately before shipment, and the camera module is shipped out as a good product. If the camera module is subjected to vibration or impact during transport after the shipment, the dust temporarily staying can move and attach to the optical path, which would lead to a defect in image at a destination (i.e. a wholesaler who, for example, sells mobile phones with a built-in camera).
One of conventional approaches to these kinds of image defects is to screening out the dust attaching to camera module components at the time of the delivery of the components. Depending on how firmly the dust is attaching, the dust may be blown off by air or washed off in water using ultrasonic waves or in HFE (hydrofluoroether).
Attempts are also being made to raise the cleanliness level of manufacturing lines to prevent dust produced during manufacture from attaching to camera module components. An example is manufacturing in a clean room which is shielded from outside.
However, a clean room would require investment in infrastructure and maintenance (cleaning of equipment and replacement of worn-out components). Large expenses should be expected to cover the installation and maintenance of the clean room and air circulation facilities (air curtains, air circulators, filtering and washing facilities, etc.). Furthermore, even if dust is successfully prevented from going inside the camera module during the assembly of the module in the clean room as above, there are nowadays possibilities of dust being produced inside the camera module while in use. Merely ensuring the cleanliness level during manufacture is insufficient to eliminate dust.
Patent Literatures 1 to 4 disclose solid-state image sensing devices in which image defect-causing dust is caught up in adhesive material.
FIG. 17 is a cross-sectional view of a solid-state image sensing device disclosed in Patent Literature 1. In this structure, an adhesive material 115 is applied in the space formed by a package 111, a solid-state image sensing element 112, and a sealing window glass 114 (internal wall faces of the package 111). The adhesive material 115 catches dust 113 produced in the space. The solid-state image sensing devices of Patent Literatures 2 and 3 have a similar structure.
FIG. 18 is a cross-sectional view of a solid-state image sensing device disclosed in Patent Literature 4. In this structure, a static charged film 230 is disposed inside a space 220 formed by a concave section 218 of a lens holder 216 and a substrate 202. An adhesive material 234 is further disposed on the charged film 230 so that it is exposed in the space 220. Dust 232 is attracted electrostatically by the charged film 230 and then caught up by the adhesive material 234.